Field of the Invention
The present invention generally relates to an imaging apparatus, and in particular it relates to a focus detection apparatus having a plurality of focus detection regions suitable for an imaging apparatus, such as a photographing camera.
Description of the Related Art
In many cases, a single-lens reflex (SLR) camera is equipped with a focus detection system employing a phase difference detection method. The phase difference detection method detects a focus state (a defocus amount) of a shooting optical system provided in an interchangeable lens, based on a phase difference between a pair of images formed by light passing through the shooting optical system. In the phase difference detection method, an in-focus position may not be accurately detected due to, for example, environmental influence during shooting, or influence of manufacturing errors of the single-lens reflex camera and the interchangeable lens.
To address such inaccuracies, Japanese Patent Application Laid-Open No. 2005-227639 discusses an imaging apparatus having a function of allowing a user to arbitrarily make a fine adjustment to an adjustment value of an automatic focusing (AF) function (i.e., AF microadjustment). However, according to the apparatus discussed in Japanese Patent Application Laid-Open No. 2005-227639, the user is required to manually repeat work for shooting and check to confirm whether a result of the fine adjustment made by the user is appropriate.
In connection the user's burden, a method for setting an adjustment value with simpler work has been discussed. Japanese Patent Application Laid-Open No. 2005-109621 discusses an imaging apparatus that captures images with different focus states (performs a focus bracket shooting), and calculates an AF correction amount (an adjustment value) based on a focus position displacement amount associated with an image selected by a user from the captured images.
In Japanese Patent Application Laid-Open No. 2005-109621, the captured image includes an error in a focus-state detection result (a distance measurement result) and an error in driving for a focus position shift amount, and thus the calculated AF correction amount may not be appropriate. In addition, in Japanese Patent Application Laid-Open No. 2005-109621, to set the AF correction amount for all distance measurement points (focus detection regions), it is necessary to calculate the AF correction amount by performing the focus bracket shooting for each of the distance measurement points. Therefore, as the number of distance measurement points increases, more work is necessary.